This invention relates to tamper-resistant closures for containers and to tamper-resistant container assemblies. For quite a number of years we have been making and selling containers, under our Registered Trade Mark SECURITAINER, covered by our British Pat. No. 1246971. Our SECURITAINER containers (hereinafter called packs) have proved to be very effective and have had a considerable commercial success and we believe the SECURITAINER pack to be the best pack of its kind on the market. On the other hand the very success of the SECURITAINER pack has meant that the pack has been used in many different industries for packing a wide variety of products and this has led to the identification of one or two problems which in turn has led us to carry out a series of investigative experiments and long-term development to see whether we could find solutions.
The problems that customers have referred to us may be summarized as follows:
1. Some customers have had difficulty when automatically packing or stacking existing SECURITAINER packs into cartons for transport and/or storage. This difficulty is due to the fact that each pack has a protruding thumb tab and tear tab on the closure. If a filled and sealed SECURITAINER pack be pushed "head first" into an outer carton then the ramp above the thumb tab in the current design generally guides the thumb tab--with the tear tab partially shielded below it--into the carton, so that the pack does not "catch" on the edge of the carton. Even if the two tabs be dead in line with the centre line of the carton wall the web and thumb tab will usually push the carton into a bowed shape so that the entire pack will be pushed in--albeit distorting the carton somewhat in the process. The problem comes when the packs are fed bottom or "feet first" into the carton, which is really the normal way of feeding in the packs. When this method of feeding in is adopted the tear tab and the thumb tab above it present a hooked surface to the carton and a pack may "catch" or snag on the edge of the carton in such a way that continued pushing will or may damage the carton or even the pack. In other words in the existing design of SECURITAINER packs the tear tab not only projects sideways so as to be easily gripped by the user but it also projects donwardly and thus presents, what we have referred to above as a hooked surface, to the carton. PA0 2. Some customers, whose products need special protection against moisture, are finding that the existing design of SECURITAINER pack does not achieve a sufficiently consistent Moisture Vapour Transmission (MVT) performance. This can sometimes be a critical factor especially with medical products and essentially this is a sealing problem. PA0 3. In the world that is becoming ever more conscious of the need for effective tamper-resistance there has been some criticism of the tamper-resistant qualities of the existing SECURITAINER pack especially the larger sizes. Due to problems of scale it has proved feasible for dexterous people to remove or persuade the entire cap off an existing large size SECURITAINER body and to replace the cap without leaving evidence of removal. This can be only partially, though not completely, overcome by changing the material formulation to give a stiffer grade and so a stiffer product. PA0 4. For similar reasons of scale, it can sometimes be difficult and indeed painful to remove the cap from a small size of SECURITAINER pack. One only has to imagine the problems and discomfort of a Nurse doing her ward round and having to remove a dozen or so of these caps in a half hour or so period of dispensing tablets to patients. PA0 5. Some customers have noted that with the existing design of SECURITAINER pack there is an inconsistent reclosure performance in the sense that some caps are almost too easy to put back on, others are reluctant to clip on properly and yet others are too difficult to put back on. This difficulty is again associated with problems of size and scale. PA0 6. The reclosure problem and a problem of cap retention is connected to some extent with a manufacturing difficulty with the existing design of cap in which the precise position of the upper membrane or weakened line is somewhat critical. We have found that it is difficult to maintain the desired degree of accuracy in the position of the upper membrane so that if the resultant "clip over" is too thin then cap retention is tenuous and if the "clip over" be too thick then cap retention is too strong. By "clip over" we mean the engagement of the cap with the annular retention bead on the body. For correct reclosure the positon of the upper membrane on the cap relative to the annular bead on the body is critical and it is difficult to allow sufficient manufacturing tolerance.
We repeat that the existing form of SECURITAINER pack is extremely successful and the problems which we have highlighted above are relatively minor compared with the undoubted advantages of the SECURITAINER pack as compared with other packs now available. Nevertheless it would be advantageous to improve our SECURITAINER packs and it is the object of this invention to do just that,